BRUSSELS — The European Union is pushing for a more stable financial system by clamping down on "shadow banking" — the high-finance sector that handles trillions of dollars but isn't bound by the same rules as banks.

The Commission, the EU's executive arm, said Wednesday that while investment vehicles such as money market funds or hedge funds are welcome because they provide extra sources of financing for companies and the economy, they can also pose serious threats to long-term financial stability.